This invention relates to triglyceride oil adducts useful in the preparation of clear, alkyd coating compositions, and to coating compositions prepared therefrom.
2. Description of the Prior Art
Alkyds containing triglyceride oil fatty acids have long been important as vehicles in protective coatings for exterior use on wood and other materials. Improvement of certain of their durability properties, including resistance to checking, cracking, flaking, erosion, and others, has been attempted by chemical modification of the basic alkyd.
For example, Miller et al. [J. Amer. Oil Chem. Soc. 39(3): 173-176 (1962)] teaches cyclization of linseed oil fatty acids and modification of alkyd resins therewith. Films prepared from these resins compared favorably with natural acid resins but only when the modifier contained relatively high levels (ca. 78%) of pure cyclic acids.
Another approach was taken by Gast et al., U.S. Pat. No. 3,485,779 and Gast et al., J. Amer. Oil Chem. Soc. 46(7): 360-364 (1969). These references teach the preparation of coating compositions by the modification of vegetable oils to urethane polyesteramides. These were prepared by first converting the vegetable oils with excess diethanolamine to their corresponding N,N-bis (2)-hydroxyethyl fatty amides and glycerol. The isolated amides were then reacted with dibasic acids or anhydrides at 140.degree.-150.degree. C. for 6-24 hours to yield the hydroxy-terminated polyestermides, which were finally modified with diisocyanate. Schneider et al., J. Paint Technol. 44(575): 58-63 (1972) later demonstrated a feasible commercial method to prepare the urethane polyesteramides in which the isolation of the intermediate hydroxyamides is eliminated. Nonetheless, the complexity of the procedure reduces the commercial attractiveness of the resulting coating compositions.
Likewise, other attempts to improve the durability of clear coatings by modification of the oil vehicles have met with only limited success.